Coxiella burnetii effector CvpB modulates phosphoinositide metabolism for optimal vacuole development
07 Jun 2016-Proceedings of the National Academy of Sciences of the United States of America (National Acad Sciences)-Vol. 113, Iss: 23
TL;DR: Coxiella vacuolar protein B (CvpB) is described as a Coxiella effector that interacts with phosphoinositides on host cell membranes and manipulates phosphatidylinositol 3-phosphate [PI(3)P] metabolism for optimalcoxiella-containing vacuole (CCV) development.
Abstract: The Q fever bacterium Coxiella burnetii replicates inside host cells within a large Coxiella-containing vacuole (CCV) whose biogenesis relies on the Dot/Icm-dependent secretion of bacterial effectors. Several membrane trafficking pathways contribute membranes, proteins, and lipids for CCV biogenesis. These include the endocytic and autophagy pathways, which are characterized by phosphatidylinositol 3-phosphate [PI(3)P]-positive membranes. Here we show that the C. burnetii secreted effector Coxiella vacuolar protein B (CvpB) binds PI(3)P and phosphatidylserine (PS) on CCVs and early endosomal compartments and perturbs the activity of the phosphatidylinositol 5-kinase PIKfyve to manipulate PI(3)P metabolism. CvpB association to early endosome triggers vacuolation and clustering, leading to the channeling of large PI(3)P-positive membranes to CCVs for vacuole expansion. At CCVs, CvpB binding to early endosome- and autophagy-derived PI(3)P and the concomitant inhibition of PIKfyve favor the association of the autophagosomal machinery to CCVs for optimal homotypic fusion of the Coxiella-containing compartments. The importance of manipulating PI(3)P metabolism is highlighted by mutations in cvpB resulting in a multivacuolar phenotype, rescuable by gene complementation, indicative of a defect in CCV biogenesis. Using the insect model Galleria mellonella, we demonstrate the in vivo relevance of defective CCV biogenesis by highlighting an attenuated virulence phenotype associated with cvpB mutations.
Citations
More filters
TL;DR: This Review explores Dot/Icm effectors from L. pneumophila and C. burnetii as key virulence factors, and examines the biochemical and cell biological functions of these effectors and their roles in the understanding of bacterial virulence.
Abstract: Legionella pneumophila and Coxiella burnetii are two evolutionarily related intracellular pathogens that use the Dot/Icm type IV secretion system to translocate effectors into host cells. These effectors are essential for the establishment of membrane-bound compartments known as replication vacuoles, which enable the survival and replication of bacteria inside host cells. The effectors interfere with diverse signalling pathways to co-opt host processes, such as vesicle trafficking, ubiquitylation, gene expression and lipid metabolism, to promote pathogen survival. In this Review, we explore Dot/Icm effectors from L. pneumophila and C. burnetii as key virulence factors, and we examine the biochemical and cell biological functions of these effectors and their roles in our understanding of bacterial virulence.
189 citations
TL;DR: The proposed role of PI3P during autophagy is discussed, notably during the autophagosome biogenesis sequence, which was recently confirmed by the demonstration thatPI3P‐binding proteins participate in the complex sequence of signalling that results in autophagous assembly and activity.
Abstract: Phosphatidylinositol-3-phosphate (PI3P) is a key player in membrane dynamics and trafficking regulation. Most PI3P is associated with endosomal membranes and with the autophagosome preassembly machinery, presumably at the endoplasmic reticulum. The enzyme responsible for most PI3P synthesis, VPS34 and proteins such as Beclin1 and ATG14L that regulate PI3P levels are positive modulators of autophagy initiation. It had been assumed that a local PI3P pool was present at autophagosomes and preautophagosomal structures, such as the omegasome and the phagophore. This was recently confirmed by the demonstration that PI3P-binding proteins participate in the complex sequence of signalling that results in autophagosome assembly and activity. Here we summarize the historical discoveries of PI3P lipid kinase involvement in autophagy, and we discuss the proposed role of PI3P during autophagy, notably during the autophagosome biogenesis sequence.
147 citations
TL;DR: This review will discuss how bacterial effector proteins from Coxiella burnetii, Brucella abortus, Salmonella enterica serovar Typhimurium, Legionella pneumophila, Chlamydia trachomatis, and Orientia tsutsugamushi manipulate the endocytic and secretory pathways.
Abstract: Intracellular bacteria have developed numerous strategies to hijack host vesicular trafficking pathways to form their unique replicative niches. To promote intracellular replication, the bacteria must interact with host organelles and modulate host signaling pathways to acquire nutrients and membrane for the growing parasitophorous vacuole all while suppressing activation of the immune response. To facilitate host cell subversion, bacterial pathogens use specialized secretion systems to deliver bacterial virulence factors, termed effectors, into the host cell that mimic, agonize, and/or antagonize the function of host proteins. In this review we will discuss how bacterial effector proteins from Coxiella burnetii, Brucella abortus, Salmonella enterica serovar Typhimurium, Legionella pneumophila, Chlamydia trachomatis, and Orientia tsutsugamushi manipulate the endocytic and secretory pathways. Understanding how bacterial effector proteins manipulate host processes not only gives us keen insight into bacterial pathogenesis, but also enhances our understanding of how eukaryotic membrane trafficking is regulated.
142 citations
Cites background from "Coxiella burnetii effector CvpB mod..."
...Similar defects in CCV fusion are noted when the essential autophagy proteins ATG5 and ATG12 are silenced, suggesting that autophagy is important for homotypic fusion of CCVs and CvpB/Cig2 may target this pathway (Newton et al., 2014)....
[...]
...Between 8 h and 2 d post-infection the CCV undergoes homotypic fusion with other CCVs and heterotypic fusion with endocytic, lysosomal, and autophagosomal vesicles....
[...]
...Screening of transposon mutant libraries has identified several C. burnetii effector proteins that are required for homotypic fusion of CCVs (Newton et al., 2014)....
[...]
...These transport vesicles are divided into three classes based on their protein coat: clathrin-coated vesicles (CCVs) originate at the plasma membrane or trans-Golgi face and fuse with endosomes or lysosomes; COPII-coated vesicles move cargo from the ER to the Golgi, whereas COPI-coated vesicles move between Golgi cisternae or from the cis-Golgi back to the ER (retrograde transport; Gomez-Navarro and Miller, 2016; Figure 1)....
[...]
...CvpB/Cig2 binds PI(3)P and PS and interferes with PI 5-kinase PIKfyve access to early endosomes, resulting in increased levels of PI(3)P on CCVs (Martinez et al., 2016)....
[...]
TL;DR: This review evaluates the proposed roles for xenophagy in controlling bacterial infection, highlighting the concept that successful pathogens have evolved ways to subvert or exploit this defense, minimizing the actual effectiveness of xenophagic in innate immunity.
116 citations
Cites background from "Coxiella burnetii effector CvpB mod..."
...burnetii also secretes CvpB, which manipulates PI3P metabolism, promoting replication[69]....
[...]
TL;DR: The cellular microbiology and genetics of Coxiella are highlighted and how recent technical advances now make CoxIElla a model organism to study macrophage parasitism.
Abstract: Invasion of macrophages and replication within an acidic and degradative phagolysosome-like vacuole are essential for disease pathogenesis by Coxiella burnetii, the bacterial agent of human Q fever. Previous experimental constraints imposed by the obligate intracellular nature of Coxiella limited knowledge of pathogen strategies that promote infection. Fortunately, new genetic tools facilitated by axenic culture now allow allelic exchange and transposon mutagenesis approaches for virulence gene discovery. Phenotypic screens have illuminated the critical importance of Coxiella's type 4B secretion system in host cell subversion and discovered genes encoding translocated effector proteins that manipulate critical infection events. Here, we highlight the cellular microbiology and genetics of Coxiella and how recent technical advances now make Coxiella a model organism to study macrophage parasitism.
76 citations
References
More filters
TL;DR: How do cells apply anabolic and catabolic enzymes, translocases and transporters, plus the intrinsic physical phase behaviour of lipids and their interactions with membrane proteins, to create the unique compositions and multiple functions of their individual membranes?
Abstract: Throughout the biological world, a 30 A hydrophobic film typically delimits the environments that serve as the margin between life and death for individual cells. Biochemical and biophysical findings have provided a detailed model of the composition and structure of membranes, which includes levels of dynamic organization both across the lipid bilayer (lipid asymmetry) and in the lateral dimension (lipid domains) of membranes. How do cells apply anabolic and catabolic enzymes, translocases and transporters, plus the intrinsic physical phase behaviour of lipids and their interactions with membrane proteins, to create the unique compositions and multiple functionalities of their individual membranes?
5,720 citations
"Coxiella burnetii effector CvpB mod..." refers methods in this paper
...CvpB binding to PS and PI(3)P was then validated by using an in vitro cosedimentation assay in which histidine-tagged CvpB was incubated with large unilamellar vesicles (LUVs) of lipid composition matching those found on PIP Strips at concentrations compatible with those observed in intracellular vesicles (21)....
[...]
TL;DR: It is shown that the exclusion ofPI3P from live mycobacterial phagosomes can be only transiently reversed by Ca2+ fluxes, and that live M. tuberculosis secretes a lipid phosphatase, SapM, that hydrolyzes PI3P, inhibits phagosome-late endosome fusion in vitro, and contributes to inhibition of phagosomal maturation.
Abstract: Live Mycobacterium tuberculosis persists in macrophage phagosomes by interfering with phagolysosome biogenesis. Here, using four-dimensional microscopy and in vitro assays, we report the principal difference between phagosomes containing live and dead mycobacteria. Phosphatidylinositol 3-phosphate (PI3P), a membrane trafficking regulatory lipid essential for phagosomal acquisition of lysosomal constituents, is retained on phagosomes harboring dead mycobacteria but is continuously eliminated from phagosomes with live bacilli. We show that the exclusion of PI3P from live mycobacterial phagosomes can be only transiently reversed by Ca2+ fluxes, and that live M. tuberculosis secretes a lipid phosphatase, SapM, that hydrolyzes PI3P, inhibits phagosome–late endosome fusion in vitro, and contributes to inhibition of phagosomal maturation.
515 citations
"Coxiella burnetii effector CvpB mod..." refers background in this paper
...Mycobacterium tuberculosis (35, 36) and Legionella pneumophila (37, 38) use effectors to deplete PI(3)P at the surface of their vacuoles to block phagosomal maturation and avoid fusion with degradative compartments....
[...]
TL;DR: Findings identify ManLAM as the M. tuberculosis product responsible for the inhibition of phagosomal maturation, which underlies the tuberculosis pandemic involving 2 billion people.
Abstract: The tubercle bacillus parasitizes macrophages by inhibiting phagosome maturation into the phagolysosome. This phenomenon underlies the tuberculosis pandemic involving 2 billion people. We report here how Mycobacterium tuberculosis causes phagosome maturation arrest. A glycosylated M. tuberculosis phosphatidylinositol [mannose-capped lipoarabinomannan (ManLAM)] interfered with the phagosomal acquisition of the lysosomal cargo and syntaxin 6 from the trans-Golgi network. ManLAM specifically inhibited the pathway dependent on phosphatidylinositol 3-kinase activity and phosphatidylinositol 3-phosphate-binding effectors. These findings identify ManLAM as the M. tuberculosis product responsible for the inhibition of phagosomal maturation.
498 citations
"Coxiella burnetii effector CvpB mod..." refers background in this paper
...Mycobacterium tuberculosis (35, 36) and Legionella pneumophila (37, 38) use effectors to deplete PI(3)P at the surface of their vacuoles to block phagosomal maturation and avoid fusion with degradative compartments....
[...]
TL;DR: Results show that regulated synthesis and turnover of phosphoinositides by membrane-associated phosphoinoside kinases and phosphatases spatially restrict the location of effectors critical for cellular transport processes, such as clathrin-mediated endocytosis, autophagy, phagocyTosis, macropinocytotic and biosynthetic trafficking.
498 citations
TL;DR: The cross talk between autophagy and intracellular compartments is discussed, highlighting recent exciting data about the role and regulation of the Vps34 class III phosphatidylinositol (PI) 3-kinase in autophophagy.
Abstract: Autophagy or “self-eating” is a highly conserved pathway that enables cells to degrade pieces of themselves in autolysosomes to enable their survival in times of stress, including nutrient deprivation. The formation of these degradative compartments requires cytosolic proteins, some of which are autophagy specific, as well as intracellular organelles, such as the ER and Golgi, and the endosome–lysosome system. Here we discuss the cross talk between autophagy and intracellular compartments, highlighting recent exciting data about the role and regulation of the Vps34 class III phosphatidylinositol (PI) 3-kinase in autophagy.
454 citations